Hidden in the back rooms of museums, specimens collected by scientists and explorers are both beautiful and enlightening.

By Jeremy Berlin

Walter looks comfortable. Dead for 50 years, the giant Pacific octopus is resting in a ten-gallon tank of ethanol solution, six-foot arms folded in cephalopod repose. His next-door neighbors hail from the Atlantic: a jarred colony of sea squirts, their blue-green bioluminescence long extinguished. Corals and algae bloom on a shelf. Leis of Tahitian snails dangle from hooks. Pearly shelled mussels from the Mississippi River, source of a once profitable button industry, glisten under glass.

And then there are the cabinets, all 230 of them: airtight, custom-made, climate-controlled homes to ten million mollusk specimens. Many were gathered on far-flung expeditions led by the likes of Ernest Shackleton, Meriwether Lewis and William Clark, Gifford Pinchot, and William Bartram.

Where is this storehouse of wonders? And how did we get here? The short answer first: We’re at the Academy of Natural Sciences in Philadelphia. We reached this collection via two others, up a half flight of stairs from entomology, with its teeming drawers of scarab beetles and four million other bugs culled from every country on Earth, and past a choice paleo trove—limbed fish from the Devonian period, mastodon teeth owned by Thomas Jefferson, slabs of ichthyosaur skeletons from England.

But this is no closet they’re kept in. It’s a eureka factory. When we think of discovery, explorations tend to hog the glory. Yet finding a specimen in the field is just the first step. The rest happens here, in the hidden depths of a museum, amid the meticulously cared-for collections. This is where species are described, named, labeled, and cataloged, often decades after they were gathered. Where scientists coax new secrets from old plants and animals, each dead specimen uniquely alive with physical, molecular, and isotopic data on everything from evolution to ecology, medicine to migration. Where our planet’s life is reckoned.

The academy was founded in 1812 by amateur naturalists, says its senior fellow and “resident humanist,” the author and historian Robert McCracken Peck. That makes it the oldest natural history museum in the Western Hemisphere, and among the first to foster an egalitarian pursuit of knowledge. So it’s the perfect place to start our search for the longer answer.

People have always collected things. Whether a vestige of our hunter-gatherer days, a need to forge order amid chaos, or a simple desire to have and to hold, the urge to possess is a hallmark of the human psyche. Yet pathology is a danger. Compulsive hoarders find value in everything. Others fixate on a single thing, succumbing to what author Nicholas Basbanes calls “a gentle madness.” In 1869 the bibliophile Sir Thomas Phillipps said he needed “to have one copy of every book in the world.” His final tally (50,000 books, perhaps 100,000 manuscripts) wasn’t bad. Or close. For zealots, wrote the evolutionary theorist Stephen Jay Gould, “the passion for collecting is a full-time job, a kind of blessed obsession.”

That obsession seeds our story. In the 16th century, with Renaissance Europe awake to the wider world, status-conscious royals and nobles (think Habsburgs and the Medici), as well as physicians and apothecaries, began assembling eclectic objects in a single room. Called Wunderkammern, or cabinets of curiosity, they broadly expressed the beautiful, the monstrous, and the exotic: preserved flora and fauna, scientific instruments, objets d’art, genetic mutations.

“A good Wunderkammer would have a stuffed crocodile, a decent mummy, a fetus in a bottle (preferably with two heads), gems and minerals and fossils, Aztec headdresses or Japanese ceremonial swords, oil paintings, and antique sculptures,” says the scholar Terry Belanger, catalog co-author for a recent Manhattan exhibit curated by collector Florence Fearrington.

In other words, these ancestors of modern museums (and P. T. Barnum’s freak shows) were odes to idiosyncrasy, not science. Enter Carl Linnaeus, a Swedish botanist with an ardor for order. “The first step in wisdom is to know the things themselves,” he wrote. To do so in a “simple, beautiful, and instructive” way, he devised a system of classification for all living things: two-word names in Latin identifying first the genus, then the species. Since 1753 his universal taxonomy “has been to scientists what the Dewey decimal system is to librarians,” says Ted Daeschler, paleontologist and vice president of collections at the academy.

Linnaeus and the Enlightenment paved the way for proper scientific collecting, says Peck, as well as for the 19th-century transition from private to public collections. Naturalists began to prepare specimens with care and rigor. But early preservation techniques could do more harm than good: Insects might be pickled in spirits, snakes crammed with straw, shells boiled and shipped in sawdust. They could also be toxic. “It is a very Arsenicy job,” wrote ornithologist John Cassin in an 1848 letter. “I labeled about half the [owl] collection … and was taken with congestion of the lungs and most violent head ache and fever.”

This is “where our culture keeps its three-dimensional knowledge of the natural world,” says Kirk Johnson, director of the Smithsonian’s National Museum of Natural History and its 126 million specimens. “People call this place America’s Attic. But it’s more like Fort Knox—a place where we keep treasures, not the crap you don’t want to deal with. It’s a vault, a temple.”

And a time machine. Using data from bird fossils, Smithsonian ornithologist Helen James is discovering now extinct island species; to date she’s described nearly 40 from Hawaii alone. Karin Bruwelheide, her colleague in forensic anthropology, is investigating the mysterious death of a 19th-century naturalist named Robert Kennicott. Since opening his iron coffin 12 years ago, her team has deduced that he died at 31 of a heart attack, his short life of cricket frog collecting plagued by poor health and bad teeth.

Johnson says cutting-edge work like that is becoming increasingly collaborative thanks to the digitization of collections, which allows museums to catalog specimens, scientists to exchange information, and the public to access that information remotely. “Now,” he says, “you can be a Maasai warrior with an iPhone and look at a collection.”

Not that it’s a replacement for the real thing. “You need both physical and digital collections,” says Daeschler. “The latter augments the former. A digital sample is just a voucher. Each specimen is the definition of that organism at that time in that place. You can’t represent it with just words or images.” Or as Peck puts it, “If we didn’t have 18 million specimens here but had 18 million pictures of those specimens, I’m not sure anyone would really care.”

Johnson agrees. “Darwin’s big insight is that all living things are related to each other,” he says. “And that story is manifestly told by museum collections. Some of these species are extinct. But we’ve got their DNA right here. We’re the keepers of the planet’s knowledge.”

Jeremy Berlin is an editor at the magazine. Rosamond Purcell’s most recent photographic books are A Glorious Enterprise and Egg and Nest.